A. Copper
B. Aluminium
C. Steel
D. Cast-iron
Related Mcqs:
- Which of the following problem arises in D.C. motors which are fed from thyristor bridge circuits ?
A. Increased I R losses
B. Increased core losses
C. Poor commutation
D. Change in motor parameters
E. All of the above - Which of the following in an application of D.C. motors?
A. Traction
B. Drives for process industry
C. Battery driven vehicles
D. Automatic control
E. All of the above - In induction motors, the length of air gap in kept as small as mechanically possible is order to have____________?
A. low power factor
B. high power factor
C. high over load capacity
D. any of the above - In self cooled motors the cooling time constant is about ___________ than the heating time constant because cooling conditions are worse at standstill?
A. 2 to 3 times greater
B. 3 to 4 times greater
C. 4 to 5 times greater
D. none of the above - For large power transformers, self oil cooled type or air blast type which of the following values of current density may be used?
A. 1.0 to 1.2 A/mm2
B. 1.5 to 2.0 A/mm2
C. 2.2 to 3.2 A/mm2
D. 3.2 to 4.2 A/mm2 - Materials exhibiting zero value of resistivity are known as ____________ ?
A. conductors
B. semiconductors
C. insulators
D. superconductors - The operation of a D.C. machine with large air gap lengths is comparatively_____________?
A. quiet
B. noisy
C. either of the above
D. none of the above - D.C. machines designed with a large value of air gap length have_____________?
A. worst, ventilation
B. poor ventilation
C. better ventilation
D. none of the above - A current density of __________ is ilsed for large power transformers with forced circulation of oil or with water cooling coils?
A. 1.5 to 2.5 A/mm2
B. 3.5 to 4.5 A/mm2
C. 4.0 to 5.0 A/mm2
D. 5.4 to 6.2 A/mm2 - For 275 kV transformers, using cold rolled grain oriented steel, which of the following values of flux density may be used?
A. 1.0 Wb/m2
B. 1.1 Wb/m2
C. 1.3 Wb/m2
D. 1.6 Wb/m2
E. None of the above
